{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,12]],"date-time":"2025-10-12T01:48:08Z","timestamp":1760233688224,"version":"build-2065373602"},"reference-count":47,"publisher":"MDPI AG","issue":"4","license":[{"start":{"date-parts":[[2021,2,9]],"date-time":"2021-02-09T00:00:00Z","timestamp":1612828800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>The two-parameter-fitting method (PFM) is commonly used to calculate the stopping-power ratio (SPR). This study proposes a new formalism: a three-PFM, which can be used in multiple spectral computed tomography (CT). Using a photon-counting CT system, seven rod-shaped samples of aluminium, graphite, and poly(methyl methacrylate) (PMMA), and four types of biological phantom materials were placed in a water-filled sample holder. The X-ray tube voltage and current were set at 150 kV and 40 \u03bc\u03bcA respectively, and four CT images were obtained at four threshold settings. A semi-empirical correction method that corrects the difference between the CT values from the photon-counting CT images and theoretical values in each spectral region was also introduced. Both the two- and three-PFMs were used to calculate the effective atomic number and electron density from multiple CT numbers. The mean excitation energy was calculated via parameterisation with the effective atomic number, and the SPR was then calculated from the calculated electron density and mean excitation energy. Then, the SPRs from both methods were compared with the theoretical values. To estimate the noise level of the CT numbers obtained from the photon-counting CT, CT numbers, including noise, were simulated to evaluate the robustness of the aforementioned PFMs. For the aluminium and graphite, the maximum relative errors for the SPRs calculated using the two-PFM and three-PFM were 17.1% and 7.1%, respectively. For the PMMA and biological phantom materials, the maximum relative errors for the SPRs calculated using the two-PFM and three-PFM were 5.5% and 2.0%, respectively. It was concluded that the three-PFM, compared with the two-PFM, can yield SPRs that are closer to the theoretical values and is less affected by noise.<\/jats:p>","DOI":"10.3390\/s21041215","type":"journal-article","created":{"date-parts":[[2021,2,10]],"date-time":"2021-02-10T04:33:46Z","timestamp":1612931626000},"page":"1215","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":3,"title":["Calculation of Stopping-Power Ratio from Multiple CT Numbers Using Photon-Counting CT System: Two- and Three-Parameter-Fitting Method"],"prefix":"10.3390","volume":"21","author":[{"given":"Sung Hyun","family":"Lee","sequence":"first","affiliation":[{"name":"Heavy Ion Beam Medical Physics and Biology, Graduate School of Medicine, Gunma University, Maebashi 371-8511, Gunma, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Naoki","family":"Sunaguchi","sequence":"additional","affiliation":[{"name":"Graduate School of Medicine, Nagoya University, Nagoya 461-8673, Aichi, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Akie","family":"Nagao","sequence":"additional","affiliation":[{"name":"Department of Electronics and Informatics, Gunma University, Kiryu 376-8515, Gunma, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Yoshiyuki","family":"Hirano","sequence":"additional","affiliation":[{"name":"Graduate School of Medicine, Nagoya University, Nagoya 461-8673, Aichi, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8132-8723","authenticated-orcid":false,"given":"Hiroshi","family":"Sakurai","sequence":"additional","affiliation":[{"name":"Department of Electronics and Informatics, Gunma University, Kiryu 376-8515, Gunma, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Yosuke","family":"Kano","sequence":"additional","affiliation":[{"name":"GHMC Group, Accelerator Engineering Corporation, Inage, Chiba 263-0043, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Masami","family":"Torikoshi","sequence":"additional","affiliation":[{"name":"Gunma University Heavy Ion Medical Center, Gunma University, Maebashi 371-8511, Gunma, Japan"},{"name":"Department of Accelerator and Medical Physics, National Institute of Radiological Sciences, Anagawa Inage-ku, Chiba 263-8555, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Tatsuaki","family":"Kanai","sequence":"additional","affiliation":[{"name":"Gunma University Heavy Ion Medical Center, Gunma University, Maebashi 371-8511, Gunma, Japan"},{"name":"Osaka Heavy Ion Therapy Center, Osaka 540-0008, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3253-0527","authenticated-orcid":false,"given":"Mutsumi","family":"Tashiro","sequence":"additional","affiliation":[{"name":"Heavy Ion Beam Medical Physics and Biology, Graduate School of Medicine, Gunma University, Maebashi 371-8511, Gunma, Japan"},{"name":"Gunma University Heavy Ion Medical Center, Gunma University, Maebashi 371-8511, Gunma, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2021,2,9]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"15","DOI":"10.1007\/BF00327253","article-title":"Measurement of effective atomic number and electron density using an EMI scanner","volume":"11","author":"Rutherford","year":"1976","journal-title":"Neuroradiology"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"169","DOI":"10.1016\/0370-1573(81)90014-4","article-title":"X-ray attenuation coefficients of elements and mixtures","volume":"70","author":"Jackson","year":"1981","journal-title":"Phys. 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